The present invention relates to a vehicle lamp lens having refractive-type step blocks and linearly transmitting-type step blocks intermixed with one another.
As shown in FIGS. 6 and 7, conventionally a Fresnel lens has been employed as an inner lens 50 for use in various vehicle signal and illumination lamps, the Fresnel lens having linearly transmitting-type step blocks 51 at its peripheral portion and refractive-type step blocks 52 at its central portion. The step blocks 51 and 52 are arranged in a concentric, intermixed manner. In a vehicle lamp lens of a double-lens construction in which an outer lens 53 is disposed forward of the front face of the inner lens 50 in opposed relation & thereto, fisheye steps 54 are formed on either the reverse face of the outer lens 53, as illustrated in FIG. 7, or on the front face of the inner lens 50 so as to enhance the diffusion or scattering of illuminating light rays emitted from a light source 55 such as a bulb.
Fisheye steps 54, however, can generally be observed as a lattice-like configuration at the front face of the lens. On the other hand, because the linearly transmitting-type step blocks 51 and refractive-type step blocks 52 of the inner lens 50 corresponding to the fisheye steps 54 are arranged in a concentric manner, a brightness difference develops at the boundary B between the linearly transmitting-type step blocks 52 and the refractive-type step blocks 51 on the surface of the inner lens 50 due to their differing light-transmitting properties or efficiencies. Therefore, when the lamp is lit, & the boundary B between the linearly transmitting-type step blocks 51 and the refractive-type step blocks 52 forms a dark area or portion C on the surface of the inner lens 50 (FIG. 6). As a result, the dark portion C is projected onto the fisheye steps 54, which detracts from the appearance of the lamp as viewed from the front side of the lens.
Therefore, as shown in FIG. 8, there has conventionally been employed an inner lens 50 of the type in which refractivetype step blocks 52, constituting a given illumination area, are made square or rectangular in conformity with the latticelike configuration of the fishey steps 54 on the outer lens 53. Thus, the dark portion C, formed at the boundary between the linearly transmitting-type step blocks 51 and refractive-type step blocks 52 of the inner lens 50, corresponds to the lattice-like boundary of the fisheye steps 54 formed on the outer lens 53, thereby reducing the undesirable optical effects produced by the dark portion C. However, to manufacture the inner lens 50 having such linearly transmitting-type step blocks 51 and refractive-type step blocks 52, the step blocks 51 and 52 are first individually molded using separate molds, and thereafter the molded blocks are combined into a unitary construction of the so-called insert type (the insert being indicated by an arrow D). As a result, the manufacturing cost of the inner lens 50 is high. Moreover, since it is rather difficult to prepare an insert mold of a s complicated shape, Only a simple shape such as a square or a rectangular shape can be obtained.